Technical Field
This disclosure relates to a pointer detection sensor and a pointer detection apparatus of a capacitance type.
Description of the Related Art
In recent years, a pointer detection apparatus of the capacitance type as a system for position detection of a pointer for use with a touch panel or the like has been and is being developed actively. Among such systems, a cross point capacitance type is available which is ready for multi-touch detection capable of detecting a plurality of pointers such as a plurality of fingers at the same time.
In a pointer detection sensor of a pointer detection apparatus of the cross point capacitance type, a determined capacitance Co (fixed capacitance) is formed in regions where portions of a plurality of upper conductors Ey and a plurality of lower conductors Ex overlap, the plurality of upper conductors Ey and the plurality of lower conductors Ex being disposed in orthogonal directions to each other as viewed in a direction orthogonal to a pointing inputting face by a pointer (the region is hereinafter referred to as region of a cross point), as depicted in FIG. 28. At a position at which a pointer fg such as a finger of a user contacts with the pointing inputting face, the pointer fg is connected to the ground through the human body, and through a capacitance Cg between the human body and the ground, a capacitance Cf is formed between an upper conductor Ey and a lower conductor Ex at the position and the pointer fg. In this manner, since capacitance Cf and capacitance Cg are formed at a position at which the pointer fg contacts with the pointing inputting face, charge between the upper conductor Ey and the lower conductor Ex varies. By detecting the variation in charge, the position pointed to by the pointer on the pointing inputting face can be specified.
However, the variation in capacitance in a region of a cross point when a finger is positioned nearby is very small, and while the value of the capacitance Co between the upper conductor Ey and the lower conductor Ex is, for example, 0.5 pF, the variation in capacitance in the region of a cross point is only approximately 0.05 pF. Therefore, the margin for the detection output of the pointer with respect to noise is severe, and it is difficult to detect a pointer such as a finger with a high sensitivity. Further, there is a problem that a pointer can be detected only where the pointer is a conductor including the human body and, in such a state that a person wears a rubber glove, a finger of the person cannot be detected as a pointer.
In Patent Document 1 (Japanese Patent Laid-Open No. 2010-79791), a capacitance type inputting apparatus is disclosed which is improved in regard to the problem and can detect a pointer different from a finger or a capacitive pen.
A pointer detection sensor for the inputting apparatus of Patent Document 1 includes, as depicted in FIG. 29(A), a first substrate 2, a flexible second substrate 3 opposing to the first substrate 2 with an air layer 4 interposed there between, a first conductor 5 formed over a substantially overall area of a face of the first substrate 2 on the second substrate 3 side, and a plurality of second conductors 6 formed on a face of the second substrate 3 on the first substrate 2 side. When the second substrate 3 is not pressed by a pointer, a capacitance C1 is formed between each of the plurality of second conductors 6 and the first conductor 5 as depicted in FIG. 29(A). However, if the second substrate 3 is pressed, then since the second substrate 3 has flexibility, the second substrate 3 is deflected at the pressed position thereof to the first substrate 2 side as indicated by an arrow mark in FIG. 29(B). Consequently, the distance between the first substrate 2 and the second substrate 3 decreases, and the capacitance configured from the first conductor 5 and a second conductor 6 at the portion changes to C2 higher than C1 mentioned above. If the second substrate 3 is pressed further as depicted in FIG. 29(C), then the second conductor 6 is brought into contact with the first conductor 5 to establish a conducting state, and the pressing input at the pressed position can be settled.
In the case of Patent Document 1, there is no restriction to the pointer, and even if a person wears a rubber glove or the like, the pressed pointed position can be detected. However, according to the detection method of Patent Document 1, although the capacitance type is adopted, a pressing input is settled by detecting a state in which the second conductor 6 is brought into contact with the first conductor 5 to establish a conducting state there between. Accordingly, even if it is possible to detect the position pressed by the pointer, it is difficult to detect the pressing force of the pointer to the second substrate 3 with a high degree of accuracy.
In Patent Document 2 (Japanese Patent Laid-Open No. 2013-20370), a pointer detection sensor and a pointer detection apparatus which solve the problem just described are provided. In the pointer detection sensor disclosed in Patent Document 2, a spacer Sp is disposed in each of regions different from overlapping regions between a plurality of upper conductors 7x and a plurality of lower conductors 7y disposed in orthogonal directions to each other as depicted in FIGS. 30(A) and 30(B). Consequently, the regions of the cross points are delimited by the spacers Sp, and therefore, pressing by a pointer in the region of each cross point can be detected accurately.
As depicted in FIG. 30(A), the conductors 7x and the conductors 7y are formed on mutually opposing faces of an upper side transparent glass substrate 8U and a lower side transparent glass substrate 8L. The upper side transparent glass substrate 8U has a small thickness sufficient to allow the upper side transparent glass substrate 8U to be deflected to the lower side. Further, the spacers Sp are disposed on, for example, the lower side transparent glass substrate 8L at positions opposing to regions in which no lower conductor 7x is formed and no upper conductor 7y is formed. In other words, the spacers Sp are formed in regions in which none of the lower conductors 7x and the upper conductors 7y are formed as viewed from the upper side transparent glass substrate 8U side.
The pressing detection principle of the pointer detection sensor of Patent Document 2 depicted in FIG. 30 is such as described below with reference to FIG. 31. Here, a case in which pressing by a pointer is carried out from the upper side transparent glass substrate 8U side in FIG. 31 is described.
In particular, if the upper side transparent glass substrate 8U is not contacted by the pointer as depicted in FIG. 31(A), then the capacitance (initial capacitance) generated between an upper conductor 7x and a lower conductor 7y is as low as, for example, approximately 1 to 2 pF. Then, if the pointer is pressed against the upper side transparent glass substrate 8U as depicted in FIG. 31(B) to apply pressing of a middle level to the upper side transparent glass substrate 8U, then the distance between the upper conductor 7x and the lower conductor 7y decreases. Thus, the capacitance between the upper conductor 7x and the lower conductor 7y between which the distance decreases in this manner varies and becomes, for example, approximately 5 to 6 pF. Then, if pressing is applied further to the upper side transparent glass substrate 8U as depicted in FIG. 31(C), then the distance between the upper conductor 7x and the lower conductor 7y at the portion at which the pressing is applied further decreases. Consequently, the capacitance between the upper conductor 7x and the lower conductor 7y varies by a great amount and becomes, for example, approximately 10 pF.
By detecting a variation in capacitance between the upper conductor 7x and the lower conductor 7y in the region of each cross point in such a manner as described above, the pressing in the region of each cross point can be detected.